Novel carbonyliridium and -rhodium complexes containing 2,6-bis[(4′S)-4′-isopropyloxazolin-2′-yl]pyridine (iPr-pybox) and 2,6-Bis[(4′R)-4′-phenyloxazolin-2′-yl]pyridine (Ph-pybox) ligands

Article abstract of DOI:10.1002/ejic.200500680

The iridium(I) complexes [Ir(CO)(κ³-N,N,N-R-pybox)] [PF₆] [R-pybox = (S,S)-iPr-pybox (1), (R,R)-Ph-pybox (2)] have been prepared by reaction of their precursor complexes [Ir(η²-C ₂H₄)₂(κ

Full text of DOI:10.1002/ejic.200500680

FULL PAPER
DOI: 10.1002/ejic.200500680
Novel Carbonyliridium and -rhodium Complexes Containing 2,6-Bis[(4ЈS)-4Ј-
isopropyloxazolin-2Ј-yl]pyridine (iPr-pybox) and 2,6-Bis[(4ЈR)-4Ј-
phenyloxazolin-2Ј-yl]pyridine (Ph-pybox) Ligands
Darío Cuervo,[a] Josefina Díez,[a] M. Pilar Gamasa,*[a] José Gimeno,[a] and
Paloma Paredes[a]
Keywords: Carbonyl complexes / Homogeneous catalysis / Iridium / N ligands / Rhodium
The iridium(
I
) complexes [Ir(CO)(κ3-N,N,N-R-pybox)][PF6]
(11)]. The treatment of complexes 1 and 2 with HCl, allyl
chloride or acyl chloride results, in most cases, in the stereo-
selective formation of the iridium(III) complexes [IrHCl(CO)-
(κ3-N,N,N-R-pybox)][PF6] [R = iPr (12), Ph (13)], [IrCl(η1-
CH2CH=CH2)(CO)(κ3-N,N,N-R-pybox)][PF6] [R = iPr (14), Ph
(15)] or [IrCl{η1-C(O)CH3}(CO)(κ3-N,N,N-R-pybox)][PF6] [R =
iPr (16), Ph (17)], respectively. The structures of derivatives
10 and 15 have been determined by single-crystal X-ray dif-
fraction analysis. The catalytic activity of monocarbonylrhod-
ium(I) and -iridium(I) complexes 1 and 3 in the hydro-
silylation and dehydrosilylation of acetophenone with di-
phenylsilane has also been examined.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
[R-pybox = (S,S)-iPr-pybox (1), (R,R)-Ph-pybox (2)] have been
prepared by reaction of their precursor complexes [Ir(η2-
C2H4)2(κ3-N,N,N-R-pybox)][PF6] (R = iPr or Ph) with carbon
monoxide. The analogous carbonylrhodium(I) complexes
[Rh(CO)(κ3-N,N,N-R-pybox)][PF6] [R-pybox = (S,S)-iPr-py-
box (3), (R,R)-Ph-pybox (4)] have been synthesised by reac-
tion of [Rh(μ-Cl)(η2-C2H4)2]2, carbon monoxide, R-pybox and
NaPF6. Complexes 1–4 undergo oxidative addition reactions
with iodine and CH3I leading, with high stereoselectivity, to
the complexes [MI(X)(CO)(κ3-N,N,N-R-pybox)][PF6] [M = Ir,
R = iPr, X = I (5); M = Rh, R = iPr, X = I (6); M = Rh, R = Ph,
X = I (7); M = Ir, R = iPr, X = CH3 (8); M = Ir, R = Ph, X = CH3
(9); M = Rh, R = iPr, X = CH3 (10); M = Rh, R = Ph, X = CH3
pyridine; R = iPr, Ph, tBu, etc.] have been shown to be-
efficient chiral ancillary ligands in transition-metal-cata-
lysed asymmetric synthesis. A recent and specific survey
discusses the state-of-the-art of this field.[1]
Introduction
In the last few years the enantiopure, tridentate nitrogen
ligands R-pybox [R-pybox = 2,6-bis(4Ј-R-oxazolin-2Ј-yl)-
Despite the importance of iridium complexes in catalytic
processes, as far as we know only a few examples of asym-
metric catalysis using [IrCl(cod)]2/pybox mixtures as the
catalyst have been described. Thus, a reductive aldol reac-
tion catalysed by [IrCl(cod)]2/indane-pybox[2] and a regio-
and enantioselective allylic substitution catalysed by mix-
[a] Instituto Universitario de Química Organometálica “Enrique
Moles” (Unidad Asociada al CSIC), Departamento de Química
Orgánica e Inorgánica, Facultad de Química, Universidad de
Oviedo,
33071 Oviedo, Spain
Fax: +34-985-103-446
E-mail: pgb@uniovi.es
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tures of [IrCl(cod)]2/phenyl-pybox and nitrogen nucleo- stirring a mixture of [Rh(μ-Cl)(η2-C2H4)2]2 (1 equiv.), R-py-
philes such as oximes, amines and hydroxylamines, have box (2 equiv.) and NaPF6 (3 equiv.) in dichloromethane/
been reported recently.[3,4] Moreover, we have just described methanol (4:1) under CO at room temperature for 1 h. The
the preparation of the first (pybox)iridium complexes,[5] na- monocarbonyl complexes [Rh(CO)(κ3-N,N,N-R-pybox)]-
mely diolefin-, dialkyne- and monocarbonyliridium(i) com- [PF6] were isolated as air-stable solids in high yields [R =
plexes (A) as well as hydrido(olefin)- and η3-allyliridium(iii) iPr (3), 91%; R = Ph (4), 84%; Scheme 2]. The preparation
derivatives (B). In light of these recent results, we decided of complexes 1 and 3 has been reported previously.[5,6]
it would be interesting to explore the synthesis of (pybox)-
iridium complexes in order to understand their properties
and eventually apply them in asymmetric catalysis. There-
fore, we report here the synthesis of novel carbonyliridi-
um(i) and -iridium(iii) complexes containing the enantio-
pure (S,S)-iPr-pybox and (R,R)-Ph-pybox ligands. This pa-
per also deals with the synthesis of the analogous carbon-
ylrhodium complexes, a type of systems that are scarcely
found in the literature.[6] Moreover, the monocarbonyl(iPr-
pybox)rhodium(i) and -iridium(i) complexes have been
tested as catalysts in the asymmetric hydrosilylation of ace-
tophenone with diphenylsilane.
Scheme 2.
Results and Discussion
Synthesis of the Complexes [M(CO)(κ3-N,N,N-R-pybox)]-
[PF6] [M = Ir, R = iPr (1), Ph (2); M = Rh, R = iPr (3),
Ph (4)]
The analytical and spectroscopic data [IR and 1H,
13C{1H} NMR] for complexes 1–4 support the proposed
formulations (see Experimental Section for details). In par-
ticular: (a) the NMR spectroscopic data are consistent with
the C2-symmetric structure of the compounds, (b) a low-
field singlet or doublet signal in the 13C{1H} NMR spectra
[δ = 182.3 (1), 173.8 (2), 191.7 (d, JC,Rh = 76.3 Hz; 3), 189.9
(d, JC,Rh = 76.3 Hz; 4) ppm] confirms the presence of the
carbonyl group, (c) the IR spectra of CH2Cl2 solutions
show a strong ν(CO) absorption band in the ranges of
1996–1989 cm–1 (for 1 and 2) and 2014–2001 cm–1 (for 3
and 4).
Since oxidative addition is one of the most typical reac-
tions of square-planar iridium(i) and rhodium(i) complexes,
a comparative study of such a process for the cationic mon-
ocarbonyliridium(i) and -rhodium(i) complexes 1–4 was
performed.
The reaction of complexes [Ir(η2-C2H4)2(κ3-N,N,N-R-
pybox)][PF6] (R = iPr[5] or Ph) with carbon monoxide
(1 atm) in dichloromethane at room temperature results in
the replacement of two ethylene molecules and the forma-
tion of the complexes [Ir(CO)(κ3-N,N,N-R-pybox)][PF6] [R
= iPr (1), Ph (2)], which were isolated as air-stable solids
in excellent yields (96% and 94%, respectively; Scheme 1).
Complexes 1 and 2 can be obtained in higher purity if a
flow of nitrogen is slowly bubbled through the dichloro-
methane solution during the reaction over 50 min and be-
fore work-up. The IR spectra in the ν(CO) region show,
along the reaction course, the initial formation of a non-
isolated dicarbonyl complex intermediate [ν(CO) = 2088,
2021 cm–1], which leads to the 16-electron monocarbonyl
complexes when the reaction mixture is worked up [ν(CO)
= 1989 (1), 1996 (2) cm–1].
Synthesis of the Complexes [MI2(CO)(κ3-N,N,N-R-
pybox)][PF6] [M = Ir, R = iPr (5); M = Rh, R = iPr (6),
Ph (7)]
Complex 1 was also isolated as the hexafluoroantimon-
ate derivative [Ir(CO){κ3-N,N,N-(S,S)-iPr-pybox}][SbF6]
(1a) after treatment of [Ir(μ-Cl)(η2-C8H14)2]2 (C8H14 = cy-
clooctene) with iPr-pybox (2 equiv.), CO (1 atm) and
The reaction of equimolar amounts of [M(CO)(κ3-
AgSbF6 (4 equiv.) in CH2Cl2 at room temperature. Simi- N,N,N-R-pybox)][PF6] (M = Ir, R = iPr; M = Rh, R = iPr,
larly, the analogous rhodium complexes were prepared by Ph) and iodine in dichloromethane at room temperature
Scheme 1.
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Scheme 3.
gives stereoselectively the complexes [IrI2(CO){κ3-N,N,N- 59.8 Hz) for the iridium and rhodium complexes, respec-
(S,S)-iPr-pybox}][PF6] (5) and [RhI2(CO)(κ3-N,N,N-R- tively.
pybox)][PF6] [R = iPr (6),[6] Ph (7)] by oxidative addition
Even though the synthesis of complexes 9–11 is com-
(Scheme 3). Complexes 5–7 were isolated as air-stable, gar- pletely stereoselective, the reaction of complex 1 with CH3I
net (5) or orange-brown (6, 7) solids in high yields (83– gives rise to the complex 8 along with a minor amount of
1
89%) and were characterised by elemental analyses and another diastereoisomer (de = 80%) according to the H
NMR spectroscopy (see Experimental Section for details). NMR spectrum of the crude reaction mixture. Since the
In particular, it must be noted that: (a) CH2Cl2 solutions of NMR and IR spectroscopic data of complexes 9–11 did not
complexes 5–7 show the ν(CO) absorption as a strong band allow us to unambiguously determine their stereochemistry,
in the range of 2125–2092 cm–1, which is at higher energy an X-ray crystal structure analysis was performed for com-
than that found for the rhodium(i) and iridium(i) precur- plex 10, which shows the expected octahedral coordination
sors 1–4 (2014–1989 cm–1), in accordance with the higher of the rhodium atom as well as a trans orientation for the
effective oxidation state of the metal atom in complexes 5– methyl and iodo ligands. Selected bond lengths and angles
7; (b) the NMR spectroscopic data for 5–7 are consistent are collected in Figure 1 (see also ref.[6] for further struc-
with the presence of the C2 symmetry axis shown by the tural data). We assume that complexes 8 (major isomer), 9
precursor complexes, thus indicating that the iodine atoms and 11 have the same stereochemistry.
are in a trans arrangement;[7] (c) a low-field signal in the
13C{1H} NMR spectra due to the carbonyl group is ob-
served as a singlet at δ = 157.8 ppm for 5 or as a doublet
at δ = 177.9–177.2 ppm (JC,Rh = 55.1–53.4 Hz) for 6 and 7.
Synthesis of the Complexes [MI(CH3)(CO)(κ3-N,N,N-R-
pybox)][PF6] [M = Ir, R = iPr (8), Ph (9); M = Rh, R =
iPr (10), Ph (11)]
The room-temperature reaction of complexes 1 and 2
with methyl iodide (1:10 molar ratio) in dichloromethane
leads to the formation of the complexes [IrI(CH3)(CO)(κ3-
N,N,N-R-pybox)][PF6] [R = iPr (8), Ph (9); Scheme 3].
However, the synthesis of analogous rhodium complexes
[RhI(CH3)(CO)(κ3-N,N,N-R-pybox)][PF6] [R = iPr (10),[6]
Ph (11)] requires the rhodium complexes 3 and 4 to be
heated at 30 °C in neat CH3I. Complexes 8–11 were isolated
Figure 1. ORTEP-type view of the molecular structure of the cation
of [RhI(CH3) (CO){κ3-N,N,N-(S,S)-iPr-pybox}][PF6] (10) drawn at
the 10% probability level. Hydrogen atoms have been omitted for
clarity. Selected bond lengths [Å] and angles [°]: Rh–N(1) 2.059(5),
Rh–N(2) 1.994(5), Rh–N(3) 2.056(5), Rh–C(1) 2.120(8), Rh–C(2)
1.900(7), Rh–I 2.7759(14), C(2)–O(1) 1.113(10); N(3)–Rh–N(1)
156.5(2).
from the reaction mixture as yellow solids in high yields [up
to 90% (8, 9) and 70–80% (10, 11)] and were characterised
by elemental analyses and NMR spectroscopy (see Experi-
mental Section for details). In particular: (a) the presence
1
of the methyl group is confirmed in the H NMR spectra
by a singlet or doublet (2JH,Rh = 1.5–1.7 Hz) in the range of
δ = 1.40–0.73 ppm; (b) this methyl carbon atom resonates in
the 13C{1H} NMR spectra at high field as a singlet or
As we have described above, monocarbonylrhodium(i)
doublet [δ = –9.5 (8), –10.9 (9), 10.3 (JC,Rh = 18.3 Hz; 10), and -iridium(i) complexes 1–4 undergo oxidative addition
9.3 (JC,Rh = 17.2 Hz; 11) ppm], while the carbonyl carbon reaction with iodine and CH3I. However, monocarbonyliri-
atom appears at low field as either a singlet or a doublet at dium(i) complexes 1 and 2 also react under mild reaction
δ = 166.8–165.1 and 185.5–184.0 ppm (JC,Rh = 60.4– conditions with HCl and allyl and acyl chloride to give the
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iridium(iii) complexes 12–17, whereas the rhodium com- Synthesis of the Complexes [IrCl(η1-CH2CH=CH2)(CO)-
plexes 3 and 4 remain unchanged under similar or stronger (κ3-N,N,N-R-pybox)][PF6] [R = iPr (14), Ph (15)] and
conditions (CH2Cl2 or refluxing MeOH). This behaviour is [IrCl{η1-C(O)CH3}(CO)(κ3-N,N,N-R-pybox)][PF6] [R =
in accordance with the well-known higher stability of iridi- iPr (16), Ph (17)]
um(iii) complexes in comparison with that of rhodium(iii)
The oxidative addition of allyl chloride and acyl chloride
complexes.[8]
to complexes 1 and 2 was also performed. Thus, the reac-
tion of 1 and 2 with allyl chloride (3 equiv.) and acyl chlo-
ride (1 equiv.) in dichloromethane at room temperature pro-
Synthesis of the Complexes [IrHCl(CO)(κ3-N,N,N-R-
duces the allyl- and acyliridium(iii) complexes 14/15 and 16/
pybox)][PF6] [R = iPr (12), Ph (13)]
17, respectively (Scheme 4). These complexes were isolated
We are particularly interested in the synthesis of hydrido as air-stable, yellow solids in 85–91% yield. Their analytic
1
complexes as they are extensively found as intermediates in and spectroscopic data (IR and H, 13C{1H} NMR) sup-
both stoichiometric and catalytic processes. The treatment port the proposed formulations (see Experimental Section
of a solution of complexes 1 and 2 in dichloromethane with for details). In particular, the following can be pointed out:
a solution of HCl in diethyl ether at room temperature gives (a) the IR spectra of 16 and 17 show the expected ν(COMe)
stereoselectively the complexes [IrClH(CO){κ3-N,N,N- absorptions of the acyl group at 1677–1669 cm–1, (b) the 1H
(S,S)-R-pybox}][PF6] [R = iPr (12), Ph (13)], which were and 13C NMR resonances of the allyl group in complexes
isolated as air-stable, yellow solids (92–94% yield; 14 and 15 are in accordance with the σ-coordination mode
Scheme 4). Complexes 12 and 13 were characterised by ele- [13C{1H} NMR spectra show the expected resonances in
mental analysis and NMR spectroscopy (see Experimental the ranges δ = 5.9–5.7 (s) and 112.9–112.1 (s) ppm for the
Section for details). The most significant features of the Cα and Cγ nuclei, respectively, of the η1-allyl group], (c) the
spectroscopic data are: (a) the characteristic ν(Ir–H) and low-field singlet signals for the carbonyl carbon nuclei of
ν(CO) IR absorptions at 2180–2164 and 2083–2075 cm–1, the acyl and carbonyl ligands in the 13C{1H} NMR spectra
respectively, (b) the high-field singlet for the hydrido ligand appear in the range δ = 196.9–196.0 and 165.9–164.1 ppm,
1
in the H NMR spectra at δ = –19.25 (12) and –19.73 (13) respectively.
ppm, and (c) the low-field singlet for the carbonyl carbon
The stereochemistry of complex 15 was confirmed by a
atom in the 13C{1H} NMR spectra at δ = 165.6 (12) and single-crystal X-ray analysis. An ORTEP view of the mol-
163.0 (13) ppm. The NMR and IR spectroscopic data are ecular structure is shown in Figure 2. Selected bond lengths
consistent with three possible stereoisomers. Unfortunately, and angles are collected in Table 1.The structure exhibits a
all attempts to crystallise complexes 12 or 13 from a distorted octahedral geometry around the iridium atom
number of solvents were unsuccessful, therefore an X-ray which is bonded to the three nitrogen atoms of the Ph-py-
analysis could not be performed. We assume that the hyd- box ligand, a chlorine atom, a carbon monoxide molecule
rido and chloro ligands are trans to each other, in a similar and an η1-allyl group (Figure 2). The chlorine atom and the
stereochemical environment to that found for complexes 10 allyl group are located in a trans disposition. The Ir–N(1)
and 15 (see below), whose structures were determined by [2.032(8) Å], Ir–N(2) [2.014(8) Å] and Ir–N(3) [2.024(10) Å]
X-ray diffraction analysis.
distances as well as the N–Ir–N [77.0(3)°, 78.6(4)° and
Scheme 4.
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155.6(4)°] bond angles fall in the range observed for the gand in complex 15 [1.117(13) Å] is comparable to that
related
complexes
[Ir(η2-C2H4)2{κ3-N,N,N-(S,S)-iPr- found in the case of the carbonylrhodium complex 10
pybox}][PF6][5] and [IrCl(η3-C3H5){κ3-N,N,N-(S,S)-iPr- [C(2)–O(1) = 1.113(10) Å]. In conclusion, both complexes
pybox}][PF6].[5] The Ir–allyl distances [Ir–C(1) = 2.118(11), 10 and 15 present the same stereochemistry, with the CO
C(1)–C(2) = 1.427(13) and C(2)–C(3) = 1.223(17) Å] are ligand trans to the pyridine nitrogen atom of the pybox li-
slightly shorter than those found for other σ-allyliridium(iii) gand (see Figures 1 and 2).
complexes such as [Ir(η1-CH2CH=CH2)3(PP2)] [PP2
=
We have recently reported the synthesis of the complex
PhP(CH2CH2PPh2)2; Ir–C(1) = 2.208(4)–2.186(4), C(1)– [IrCl(η3-C3H5){κ3-N,N,N-(S,S)-iPr-pybox}][PF6][5] by treat-
C(2) = 1.488(6)–1.463(6) and C(2)–C(3) = 1.319(6)– ment of the complex [Ir(η2-C2H4)2{κ3-N,N,N-(S,S)-iPr-
1.253(9) Å].[9] Finally, the C–O bond length of the CO li- pybox}][PF6] with allyl chloride in acetone at room tem-
perature. The reaction presumably involves the formation
of an intermediate monoolefiniridium(iii) complex with the
allyl group having a monodentate coordination. However,
complexes 14 and 15 are stable in the sense that they do not
evolve into the corresponding η3-allyl complexes [IrCl(η3-
C3H5)(κ3-N,N,N-R-pybox)][PF6] (R = iPr, Ph) by loss of
carbon monoxide.
Hydrosilylation of Acetophenone
The rhodium(iii) complexes [RhCl3(R-pybox)] (R = iPr,
sBu, tBu, etc.) were first used as catalyst precursors by Ni-
shiyama and co-workers in the enantioselective synthesis of
secondary alcohols by the asymmetric reduction of ketones
with diphenylsilane.[10] (Scheme 5). They assumed the for-
mation of a rhodium(i) complex as the active species in situ
by reduction of the precatalyst in the presence of AgBF4
and diphenylsilane.
Figure 2. ORTEP-type view of the molecular structure of the cation
of [IrCl(η1-CH2CH=CH2)(CO){κ3-N,N,N-(S,S)-iPr-pybox}][PF6]
(15) drawn at the 10% probability level. Hydrogen atoms have been
omitted for clarity.
Scheme 5.
We became interested to know the behaviour of the cat-
ionic carbonyliridium(i) and -rhodium(i) complexes re-
Table 1. Selected bond lengths [Å] and angles [°] for complex 15.
Ir–Cl
Ir–N(1)
Ir–N(2)
Ir–N(3)
Ir–C(1)
Ir–C(4)
C(1)–C(2)
C(2)–C(3)
2.470(3)
2.032(8)
2.014(8)
2.024(10)
2.118(11)
1.882(11)
1.427(13)
1.223(17)
1.117(13)
155.6(4)
77.0(3)
ported here since neither the previous reduction of the pre-
catalyst nor the use of AgBF4 as additive would be neces-
sary. Therefore, the catalytic activity of the complexes
[M(CO){κ3-N,N,N-(S,S)-iPr-pybox}][PF6] [M = Ir (1), Rh
(3)] in the hydrosilylation/reduction of acetophenone was
investigated (Scheme 6 and Table 2).
C(4)–O(3)
N(1)–Ir–N(3)
N(1)–Ir–N(2)
N(2)–Ir–N(3)
N(1)–Ir–C(4)
N(3)–Ir–C(4)
N(2)–Ir–C(4)
N(1)–Ir–C(1)
N(3)–Ir–C(1)
N(2)–Ir–C(1)
Ir–C(1)–C(2)
C(1)–C(2)–C(3)
C(4)–Ir–C(1)
Cl–Ir–C(1)
N(1)–Ir–Cl
N(2)–Ir–Cl
N(3)–Ir–Cl
O(3)–C(4)–Ir(1)
78.6(4)
103.1(4)
101.3(5)
178.7(4)
87.9(4)
92.0(4)
89.1(4)
Scheme 6.
116.2(8)
138(2)
92.2(4)
175.2(3)
91.6(2)
86.2(3)
[Ir(CO){κ3-N,N,N-(S,S)-iPr-pybox}][PF6] (1) was found
to be catalytically active, with complete conversion of the
ketone into the corresponding silyl ether at room tempera-
ture after 72 h of reaction (Table 2, entry 1). However, the
desilylation of the product led to racemic 1-phenylethanol,
which means that the reduction takes place without asym-
86.6(3)
174.6(10)
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Table 2. Hydrosilylation of acetophenone catalysed by complexes 1 has been demonstrated to be a very efficient catalyst for the
and 3.[a]
dehydro-O-silylation of acetophenone to give the silyl enol
ether PhC(OSiHPh2)=CH2 as the major product.
En- Cata- iPr-py-
Conver-
sion
Silyl
ether
[%][b]
Silyl enol
ether
T
t
try
lyst
box
[°C] [h]
18 72
0
0
[%][b]
[%][b]
Experimental Section
1
2
3
4
5
1
3
3
3
3
–
4 equiv.
–
99
99
16
30
9
–
4
3
1
100
100
100
100
84
70
91
90
General: All reactions were performed under dry nitrogen using
vacuum-line and standard Schlenk techniques. All reagents were
obtained from commercial suppliers and used without further puri-
fication. Solvents were dried by standard methods and distilled un-
der nitrogen before use. The complexes [Ir(η2-C2H4)2{κ3-N,N,N-
(S,S)-iPr-pybox}][PF6], [Ir(μ-Cl)(η2-C8H14)2]2 (C8H14 = cyclooc-
tene) and [Rh(μ-Cl)(η2-C2H4)2]2 were prepared according to pre-
viously reported methods.[5,14] Infrared spectra were recorded with
a Perkin–Elmer FT 1720-X or Paragon 1000 spectrometer. The
conductivities were measured at room temperature, for approx.
5×10–4 m acetone solutions, with a Jenway PCM3 conductimeter.
4 equiv. 18
–
18 0.5
10
[a] The reactions were carried out under conditions similar to those
reported in the literature.[11] Details of the procedure are given in
the Experimental Section. [b] The values in the last three columns
1
were calculated by integration of signals in the H NMR spectra.
metric induction. At first sight, this fact can be understood
if the iPr-pybox ligand decoordinates before the active spe-
cies is formed, otherwise some degree of induction should The C, H and N analyses were carried out with a Perkin–Elmer
240-B microanalyzer. Mass spectra (FAB) were determined with a
VG-Autospec mass spectrometer, operating in the positive mode;
3-nitrobenzyl alcohol (NBA) was used as the matrix. NMR spectra
were recorded with a Bruker AC300 (DPX-300 or AV-300) instru-
ment at 300 MHz (1H) or 75.4 MHz (13C) or a Bruker AMX-400
instrument at 400 MHz (1H) or 100.6 MHz (13C), using SiMe4 as
standard. DEPT experiments were carried out for most of the com-
plexes.
have been observed. This result contrasts with those ob-
tained with the rhodium(i) complex [Rh(CO){κ3-N,N,N-
(S,S)-iPr-pybox}][PF6] (3; Table 2, entries 2–5), since vari-
able mixtures of the expected diphenylsilyl ether (as race-
mate) and diphenylsilylenol ether are obtained when the re-
action is run either at 0 °C or at room temperature
(Scheme 6). The latter product results from the reductive
O–Si coupling between diphenylsilane and the enol tauto-
mer of the ketone. In all cases the conversion is quantitative
and the diphenylsilyl enol ether is the major reaction prod-
uct. We also found that the best selectivity in favour of the
silyl enol ether is achieved at room temperature (Table 2,
Entries 4 and 5 vs. 2 and 3) and that no excess of ligand is
required at that temperature (Entries 4 and 5). A dehydro-
genative silylation of ketones with a bifunctional organosil-
ane catalysed by a mixture of the chiral or achiral com-
plexes derived from [RhCl3(pybox)] and AgOTf was re-
ported in 1993 by Nishiyama.[11] Representative examples
of the transition-metal-catalysed dehydrogenative silylation
of ketones with hydrosilanes have been reported.[12]
Synthesis of [Ir(η2-C2H4)2{κ3-N,N,N-(R,R)-Ph-pybox}][PF6]:
A
flow of ethylene was slowly bubbled at room temperature into a
suspension of [Ir(μ-Cl)(coe)2]2 (0.448 g, 0.5 mmol) in 5 mL of meth-
anol. After the solution colour became yellow, Ph-pybox (0.369 g,
1 mmol) was added and the mixture stirred at –40 °C for 40 min.
NaPF6 (0.248 g, 1.45 mmol) was added to the resulting red solution
and the mixture stirred at –40 °C for 45 min. Diethyl ether was then
added (ca. 100 mL) and the resulting red solid was washed with
cold diethyl ether (3×5 mL) and then vacuum-dried (89% yield).
Yield: 89% (0.064 g). Colour: red. C27H27F6IrN3O2P (762.70):
calcd. C 42.52, H 3.57, N 5.51; found C 41.32, H 3.40, N 5.34.
FAB-MS: m/z = 590 [M+ – C2H4], 562 [M+ – 2 C2H4]. IR (KBr):
–
ν
˜
=
840 (PF6 ) cm–1. Conductivity (acetone, 20 °C):
1
129 Ω–1 cm2 mol–1. H NMR (300 MHz, CD2Cl2, 20 °C): δ = 8.17
(s, 3 H, C5H3N), 7.40, 7.09 (2×m, 10 H, CHPh), 5.23 (m, 2 H,
OCH2 or CHPh), 4.81 (m, 2 H, OCH2 or CHPh), 4.47 (m, 2 H,
OCH2 or CHPh), 2.33 (br., 4 H, C2H4), 1.97 (br., 4 H, C2H4) ppm.
13C{1H} NMR (75.48 MHz, CD2Cl2, 20 °C): δ = 170.09 (s, OCN),
145.66 (s, C2,6 C5H3N), 136.60 (s, C4H C5H3N), 130.31, 129.66,
128.30, 126.52 (s, C3,5H C5H3N and Ph), 79.27 (s, OCH2), 66.99 (s,
CHPh), 32.97 (s, C2H4) ppm.
In conclusion, acetophenone is easily and quantitatively
transformed into its corresponding diphenylsilyl enol ether,
at room temperature, with very high selectivity (9:1) in the
presence of 1.0 mol% of [Rh(CO){κ3-N,N,N-(S,S)-iPr-
pybox}][PF6]. Silyl enol ethers are reagents of enormous
interest in organic synthesis that take part in numerous or-
ganic transformations.[13]
Synthesis of Complexes [Ir(CO)(κ3-N,N,N-R-pybox)][X] [X = PF6,
R = iPr (1), Ph (2); X = SbF6, R = iPr (1a)]. Method A: A solution
of [Ir(η2-C2H4)2(κ3-N,N,N-R-pybox)][PF6] (R
= iPr or Ph)
Conclusions
(0.1 mmol) in dichloromethane (10 mL) was stirred at room tem-
perature under CO for 5 min. The resulting solution was then con-
centrated to about 3 mL and the residue diluted with 30 mL of
diethyl ether to yield a dark solid, which was washed with diethyl
ether (3×5 mL) and vacuum-dried. Complexes 1 and 2 were ob-
tained in higher purity if a flow of nitrogen was slowly bubbled
into the dichloromethane solution over 50 min and the mixture
worked up as above. Method B: A solution of [Ir(μ-Cl)(η2-
C8H14)2]2 (0.036 g, 0.04 mmol) in dichloromethane (10 mL) was
stirred at room temperature under CO for 5 min. iPr-pybox
(0.024 g, 0.08 mmol) and AgSbF6 (0.052 g, 0.15 mmol) were then
In summary, the synthesis of monocarbonyl derivatives
[M(CO)(κ3-N,N,N-R-pybox)][PF6] (M = Rh, Ir) containing
the enantiopure (S,S)-iPr-pybox and (R,R)-Ph-pybox li-
gands has been reported. This paper also deals with the
synthesis of new organometallic iridium(iii) and rhodi-
um(iii) complexes by stereoselective oxidative addition reac-
tions. The catalytic activity of the complexes [M(CO){κ3-
N,N,N-(S,S)-iPr-pybox}][PF6] (M = Rh, Ir) in the hydro-
silylation of acetophenone has been examined. In particu-
lar, the complex [Rh(CO){κ3-N,N,N-(S,S)-iPr-pybox}][PF6] added and the mixture was stirred in the dark for 4 h. The suspen-
604 Eur. J. Inorg. Chem. 2006, 599–608
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Carbonyliridium and -rhodium Complexes of Pybox Ligands
FULL PAPER
sion was filtered through kieselguhr and the resulting solution was
then concentrated to about 3 mL. Addition of hexane (30 mL)
yielded a dark solid, which was washed with hexane (3×5 mL) and
vacuum-dried. 1: Yield: 96% (0.064 g). Colour: dark green.
[D6]acetone, 20 °C): δ = 8.52 (t, JH,H = 8.0 Hz, 1 H, H4 C5H3N),
8.23 (d, JH,H = 8.0 Hz, 2 H, H3,5 C5H3N), 7.43 (m, 10 H, Ph), 5.47
(m, 4 H, OCH2), 4.93 (pt, JH,H = 8.6 Hz, 2 H, CHPh) ppm.
13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 189.9 (d,
JC,Rh = 76.3 Hz, CO), 168.8 (s, OCN), 147.2 and 144.4 (s, Ph and
C18H23F6IrN3O3P (666.58): calcd. C 32.43, H 3.48, N 6.30; found
C 31.85, H 3.13, N 5.81. IR (KBr): ν = 1968 (CO), 840 (PF ) C2,6 C5H3N), 139.0 (s, C4H C5H3N), 129.8, 129.7, 128.9, 126.2 (s,
–
˜
6
cm–1. IR (CH Cl ): ν = 1989 (CO) cm–1. Conductivity (acetone, Ph and C3,5H C5H3N), 80.6 (s, OCH2), 69.9 (s, CHPh) ppm.
˜
2
2
20 °C): 123 Ω–1 cm2 mol–1. 1H NMR (300 MHz, [D6]acetone,
20 °C): δ = 8.36 [t, JH,H = 8.0 Hz, 1 H, H4 C5H3N), 8.17 (d, JH,H
= 8.0 Hz, 2 H, H3,5 C5H3N), 5.16 (m, 4 H, OCH2), 4.48 (m, 2 H,
CHiPr), 2.22 (m, 2 H, CHMe2), 1.06 (d, JH,H = 7.1 Hz, 6 H,
CHMe2), 0.98 (d, JH,H = 6.8 Hz, 6 H, CHMe2) ppm. 13C{1H}
NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 182.3 (s, CO), 172.0
(s, OCN), 149.0 (s, C4H C2,6 C5H3N), 125.4 (s, C3,5H C5H3N), 74.5
(s, OCH2), 71.7 (s, CHiPr), 31.1 (s, CHMe2), 18.3 (s, CHMe2), 14.5
(s, CHMe2) ppm. 2: Yield: 94% (0.069 g). Colour: garnet.
Synthesis
of
Complex
trans-[IrI2(CO){κ3-N,N,N-(S,S)-iPr-
pybox}][PF6] (5): I2 (0.076 g, 0.30 mmol) was added to a solution
of complex 1 (0.100 g, 0.15 mmol) in 10 mL of dichloromethane.
Upon addition of iodine, the black solution turned red. The solu-
tion was stirred at room temperature for 5 min. The volume was
then reduced to about 3 mL and 30 mL of diethyl ether was added
to yield an orange solid, which was washed with diethyl ether
(2×20 mL) and dried under reduced pressure. Yield: 85% (0.125 g).
Colour: garnet. C18H23F6I2IrN3O3P (920.39): calcd. C 23.49, H
C24H19F6IrN3O3P (734.62): calcd. C 39.24, H 2.61, N 5.72; found
2.52, N 4.57; found C 24.28, H 2.68, N 4.51. IR (KBr): ν = 2102
˜
–
C 38.57, H 2.45, N 5.34. IR (KBr): ν = 1978 (CO), 842 (PF )
˜
6
(CO), 845 (PF ) cm–1. IR (CH Cl ): ν = 2092 (CO) cm–1. Conduc-
–
˜
cm–1. IR (CH Cl ): ν = 1996 (CO) cm–1. Conductivity (acetone,
6
2
2
˜
2
2
tivity (acetone, 20 °C): 128 Ω–1 cm2 mol–1. 1H NMR (300 MHz,
20 °C): 117 Ω–1 cm2 mol–1. 1H NMR (300 MHz, [D6]acetone,
20 °C): δ = 8.41 (m, 1 H, H4 C5H3N), 8.28 (d, JH,H = 8.5 Hz, 2 H,
H3,5 C5H3N), 7.43 (m, 10 H, CHPh), 5.63 (m, 2 H, OCH2), 5.48
(m, 2 H, OCH2), 5.04 (m, 2 H, CHPh) ppm. 13C{1H} NMR
(75.48 MHz, [D6]acetone, 20 °C) δ = 173.8 (s, CO), 166.1 (s, OCN),
143.5 (s, C2,6 C5H3N), 140.0 (s, C4H C5H3N), 132.0 (s, ipso-Ph),
123.6, 123.4, 122.7 (s, Ph), 118.9 (s, C3,5H C5H3N), 74.7 (s, OCH2),
65.0 (s, CHPh) ppm. 1a: Colour: very dark green. C18H23F6Ir-
[D6]acetone, 20 °C): δ = 8.90 (m, 1 H, H4 C5H3N), 8.74 (d, JH,H
=
8.0 Hz, 2 H, H3,5 C5H3N), 5.37 (m, 4 H, OCH2), 4.64 (m, 2 H,
CHiPr), 2.28 (m, 2 H, CHMe2), 1.17 (d, JH,H = 7.0 Hz, 6 H,
CHMe2), 1.13 (d, JH,H = 6.6 Hz, 6 H, CHMe2) ppm. 13C{1H}
NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 170.9 (s, OCN), 157.8
(s, CO), 145.9 (s, C4H C5H3N), 143.9 (s, C2,6 C5H3N), 130.8 (s,
C3,5H C5H3N), 75.3 (s, OCH2), 71.3 (s, CHiPr), 30.4 (s, CHMe2),
18.5 (s, CHMe2), 15.8 (s, CHMe2) ppm.
N3O3Sb (757.36): calcd. C 28.55, H 3.06, N 5.55; found C 29.06,
–
H 3.06, N 5.20. IR (KBr): ν = 1973 (CO), 659 (SbF ) cm–1. IR
Synthesis of Complexes trans-[RhI2(CO)(κ3-N,N,N-R-pybox)][PF6]
[R = iPr (6), Ph (7)]: I2 (0.044 g, 0.173 mmol) was added to a solu-
tion of complex 3 or 4 (0.173 mmol) in 10 mL of dichloromethane
or THF. The green solution turned orange. After 5 min, the volume
was reduced to about 2 mL and 30 mL of diethyl ether added,
yielding an orange-brown solid which was washed with diethyl
ether (2×20 mL) and vacuum-dried. 6: Yield: 89% (0.129 g). Col-
our: orange-brown. C18H23F6I2N3O3PRh (831.07): calcd. C 26.01,
˜
6
(CH Cl ): ν = 1989 (CO) cm–1. Conductivity (acetone, 20 °C):
˜
2
2
130 Ω–1 cm2 mol–1. 1H NMR (300 MHz, [D6]acetone, 20 °C): δ =
8.36 (t, JH,H = 8.0 Hz, 1 H, H4 C5H3N), 8.16 (d, JH,H = 8.0 Hz, 2
H, H3,5 C5H3N), 5.16 (m, 4 H, OCH2), 4.47 (m, 2 H, CHiPr), 2.24
(m, 2 H, CHMe2), 1.07 (d, JH,H = 7.2 Hz, 6 H, CHMe2), 0.99 (d,
JH,H = 6.9 Hz, 6 H, CHMe2) ppm.
Synthesis of Complexes [Rh(CO)(κ3-N,N,N-R-pybox)][PF6] [R = iPr
(3), Ph (4)]: A solution of the corresponding pybox ligand
(1.028 mmol), [Rh(μ-Cl)(η2-C2H4)2]2 (0.200 g, 0.514 mmol) and
NaPF6 (0.259 g, 1.542 mmol) in dichloromethane (20 mL)/meth-
anol (5 mL) was stirred at room temperature under CO for 1 h.
The solvent was then removed under reduced pressure and the solid
residue was extracted with dichloromethane and filtered. The re-
sulting solution was then concentrated to about 3 mL and 30 mL
of diethyl ether added to yield a solid, which was washed with
diethyl ether (2×30 mL) and vacuum-dried. 3: Yield: 91%
(0.542 g). Colour: garnet C18H23F6N3O3PRh (577.26): calcd. C
37.45, H 4.01, N 7.28; found C 37.81, H 3.96, N 7.02. FAB-MS:
H 2.79, N 5.06; found C 25.58, H 2.86, N 5.34. IR (KBr): ν =
˜
–
2110 (CO), 840 (PF ) cm–1. IR (CH Cl ): ν = 2112 (CO) cm–1.
˜
6
2
2
Conductivity (acetone, 20 °C): 122 Ω–1 cm2 mol–1. 1H NMR
(300 MHz, CD2Cl2, 20 °C): δ = 8.73 (t, JH,H = 8.1 Hz, 1 H, H4
C5H3N), 8.41 (d, JH,H = 8.1 Hz, 2 H, H3,5 C5H3N), 5.12–4.97 (m,
4 H, OCH2), 4.39 (m, 2 H, CHiPr), 2.17 (m, 2 H, CHMe2), 1.08
(d, JH,H = 6.5 Hz, 6 H, CHMe2), 1.06 (d, JH,H = 6.2 Hz, 6 H,
CHMe2) ppm. 13C{1H} NMR (75.48 MHz, CD2Cl2, 20 °C): δ =
177.9 (d, JC,Rh = 53.4 Hz, CO), 167.4 (s, OCN), 145.1 and 144.6
(2×s, C4H and C2,6 C5H3N), 130.1 (s, C3,5H C5H3N), 74.5 and
71.0 (s, OCH2 and CHiPr), 30.2 (s, CHMe2), 15.9 (s, CHMe2), 14.3
(s, CHMe2) ppm. 7: Yield: 83% (0.129 g). Colour: orange-brown.
C24H19F6I2N3O3PRh (899.10): calcd. C 32.06, H 2.13, N 4.67;
m/z = 432 [M+], 404 [M+ – CO]. IR (KBr): ν = 1981 (CO), 840
˜
(PF ) cm–1. IR (CH Cl ): ν = 2001 (CO) cm–1. Conductivity (ace-
–
˜
6
2
2
found C 32.83, H 2.33, N 4.10. IR (KBr): ν = 2125 (CO), 840
˜
tone, 20 °C): 118 Ω–1 cm2 mol–1. H NMR (300 MHz, [D6]acetone,
20 °C): δ = 8.50 (t, JH,H = 8.2 Hz, 1 H, H4 C5H3N), 8.16 (d, JH,H
= 8.2 Hz, 2 H, H3,5 C5H3N), 5.14–4.99 (m, 4 H, OCH2), 4.36 (m,
2 H, CHiPr), 2.16 (m, 2 H, CHMe2), 1.05 (d, JH,H = 6.8 Hz, 6 H,
CHMe2), 0.98 (d, JH,H = 6.8 Hz, 6 H, CHMe2) ppm. 13C{1H}
1
(PF ) cm–1. IR (CH Cl ): ν = 2125 (CO) cm–1. Conductivity (ace-
–
˜
6
2
2
tone, 20 °C): 127 Ω–1 cm2 mol–1. H NMR (300 MHz, [D6]acetone,
20 °C): δ = 8.52 (t, JH,H = 7.8 Hz, 1 H, H4 C5H3N), 8.23 (d, JH,H
= 7.8 Hz, 2 H, H3,5 C5H3N), 7.43 (m, 10 H, Ph), 5.47 (m, 4 H,
OCH2), 5.30 (m, 2 H, CHPh) ppm. 13C{1H} NMR (75.48 MHz,
[D6]acetone, 20 °C): δ = 177.2 (d, JC,Rh = 55.1 Hz, CO), 168.3 (s,
OCN), 146.0 and 145.7 (2×s, C2,6H C5H3N), 134.4 (s, C4H
C5H3N), 131.1–128.8 (Ph and C3,5H C5H3N), 80.7 (s, OCH2), 70.9
(s, CHPh) ppm.
1
NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 191.7 (d, JC,Rh
=
76.3 Hz, CO), 168.1 (s, OCN), 146.3 (s, C4H C5H3N), 144.5 (s,
C2,6 C5H3N), 125.9 (s, C3,5H C5H3N), 73.7 and 70.1 (s, OCH2 and
CHiPr), 30.9 (s, CHMe2), 18.1 (s, CHMe2) 14.5 (s, CHMe2) ppm. 4:
Yield: 84% (0.557 g). Colour: green. C24H19F6N3O3PRh (645.30):
calcd. C 44.67, H 2.96, N 6.51; found C 43.74, H 2.60, N 6.10.
Synthesis of Complexes [Ir(CH3)I(CO)(κ3-N,N,N-R-pybox)][PF6] [R
= iPr (8), Ph (9)]: Iodomethane (0.093 mL, 1.5 mmol) was added
to a solution of complex 1 or 2 (0.15 mmol) in 10 mL of dichloro-
FAB-MS: m/z = 500 [M+], 472 [M+ – CO]. IR (KBr): ν = 1997
˜
–
(CO), 840 (PF ) cm–1. IR (CH Cl ): ν = 2014 (CO) cm–1. Conduc-
˜
6
2
2
tivity (acetone, 20 °C): 130 Ω–1 cm2 mol–1. 1H NMR (300 MHz, methane. The solution was stirred at room temperature. The re-
Eur. J. Inorg. Chem. 2006, 599–608
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
605

D. Cuervo, J. Díez, M. P. Gamasa, J. Gimeno, P. Paredes
FULL PAPER
sulting orange solution was then concentrated to about 3 mL and
30 mL of a mixture of diethyl ether and hexane (1:1) was added to
yield a yellow solid, which was washed with diethyl ether (3×5 mL)
and dried under reduced pressure. 8: Reaction time: 1 h. Yield: 93%
136.2 and 135.4 (s, Ph and C4H C5H3N), 131.1–129.7 (Ph and
C3,5H C5H3N), 80.6 (s, OCH2), 80.6 (s, OCH2), 70.3 (s, CHPh),
69.9 (s, CHPh), 9.3 (d, JC,Rh = 17.2 Hz, RhMe) ppm.
Synthesis of Complexes [IrClH(CO)(κ3-N,N,N-R-pybox)][PF6] [R =
iPr (12), Ph (13)]: A solution of HCl in diethyl ether (1 m, 0.1 mL,
0.1 mmol) was added to a solution of complex 1 or 2 (0.1 mmol)
in 10 mL of dichloromethane at room temperature and the reaction
mixture was stirred. A diethyl ether/hexane (1:1) mixture was added
and the resulting yellow solid washed with the same mixture
(2×5 mL) and then vacuum-dried. 12: Reaction time: 50 min.
(0.113 g). Colour: yellow. FAB-MS: m/z = 664 [M+]. IR (KBr): ν
˜
= 2076 (CO), 840 (PF ) cm–1. IR (CH Cl ): ν = 2069 (CO) cm–1.
–
˜
6
2
2
Conductivity (acetone, 20 °C): 125 Ω–1 cm2 mol–1. 1H NMR
(300 MHz, [D6]acetone, 20 °C): δ = 8.79 (t, JH,H = 8.1 Hz, 1 H, H4
C5H3N), 8.56 (m, 2 H, H3,5 C5H3N), 5.35 (m, 4 H, OCH2), 4.66
(m, 2 H, CHiPr), 2.27 (m, 2 H, CHMe2), 1.13 (m, 9 H, CHMe2),
1.11 (s, 3 H, IrMe), 1.02 (d, JH,H = 6.7 Hz, 3 H, CHMe2) ppm.
13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C, major isomer): δ
= 170.8 (s, OCN), 170.3 (s, OCN), 166.8 (s, CO), 145.0 (s, C4H
C5H3N), 144.8 (s, C2,6 C5H3N), 144.0 (s, C2,6 C5H3N), 130.0 (s,
C3,5H C5H3N), 129.8 (s, C3,5H C5H3N), 75.2 (s, CHiPr), 75.1 (s,
CHiPr), 71.9 (s, OCH2), 71.1 (s, OCH2), 30.7 (s, CHMe2), 30.4 (s,
CHMe2), 19.2 (s, CHMe2), 19.0 (s, CHMe2), 16.4 (s, CHMe2), 15.5
(s, CHMe2), –9.5 (s, IrMe) ppm. 9: Reaction time: 20 min. Yield:
94% (0.123 g). Colour: yellow. C25H22F6IIrN3O3P (876.56): calcd.
C 34.26, H 2.53, N 4.79; found C 34.54, H 2.51, N 4.72. IR (KBr):
Yield: 92% (0.071 g). Colour: yellow. FAB-MS: m/z = 558 [M+],
–
530 [M+ – CO]. IR (KBr): ν = 2180 (Ir–H), 2063 (CO), 842 (PF )
˜
6
cm–1. IR (CH Cl ): ν = 2075 (CO) cm–1. Conductivity (acetone,
˜
2
2
20 °C): 124 Ω–1 cm2 mol–1. 1H NMR (300 MHz, [D6]acetone,
20 °C): δ = 8.82 (t, JH,H = 8.0 Hz, 1 H, H4 C5H3N), 8.54 (d, JH,H
= 8.0 Hz, 2 H, H3,5 C5H3N), 5.34 (m, 4 H, OCH2), 4.63 (m, 2 H,
CHiPr), 2.26 (m, 2 H, CHMe2), 1.12 (d, JH,H = 6.8 Hz, 9 H,
CHMe2), 0.96 (d, JH,H = 6.8 Hz, 3 H, CHMe2), –19.25 (s, 1 H,
IrH) ppm. 13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C): δ =
171.8 (s, OCN), 171.1 (s, OCN), 165.6 (s, CO), 145.6 (s, C4H
C5H3N), 145.1 (s, C2,6 C5H3N), 129.3 (s, C3,5H C5H3N), 75.1 (s,
OCH2), 74.7 (s, OCH2), 72.4 (s, CHiPr), 70.2 (s, CHiPr), 31.2 (s,
CHMe2), 30.7 (s, CHMe2), 18.7 (s, CHMe2), 18.3 (s, CHMe2), 15.8
(s, CHMe2), 14.3 (s, CHMe2) ppm. 13: Reaction time: 5 min. Yield:
94% (0.073 g). Colour: yellow. C24H20ClF6IrN3O3P (771.30): calcd.
–
ν = 2067 (CO), 842 (PF ) cm–1. IR (CH Cl ): ν = 2075 (CO) cm–1.
˜
˜
6
2
2
Conductivity (acetone, 20 °C): 119 Ω–1 cm2 mol–1. 1H NMR
(300 MHz, [D6]acetone, 20 °C): δ = 8.84 (m, 1 H, H4 C5H3N), 8.65
(m, 2 H, H3,5 C5H3N), 7.70–7.30 (2×m, 10 H, CHPh), 5.80 (m, 2
H, OCH2), 5.62 (m, 2 H, OCH2), 5.31 (m, 2 H, CHPh), 0.73 (s, 3
H, IrMe) ppm. 13C{1H} NMR (50.32 MHz, [D6]acetone, 20 °C): δ
= 170.5 (s, OCN), 170.3 (s, OCN), 165.1 (s, CO), 144.7 (s, C4H
C5H3N), 135.8 (s, C2,6 C5H3N), 135.0 (s, C2,6 C5H3N), 131.1, 130.7,
130.3, 129.7, 129.7 (s, C3,5H C5H3N, Ph), 80.5 (s, OCH2), 80.3 (s,
OCH2), 71.0 (s, CHPh), 70.7 (s, CHPh), –10.9 (s, IrMe) ppm.
C 37.38, H 2.61, N 5.45; found C 36.70, H 2.60, N 5.11. IR (KBr):
ν = 2164 (Ir–H), 2074 (CO), 843 (PF ) cm–1. IR (CH Cl ): ν =
–
˜
˜
6
2
2
2083 (CO) cm–1. Conductivity (acetone, 20 °C): 123 Ω–1 cm2 mol–1.
1H NMR (300 MHz, [D6]acetone, 20 °C): δ = 8.84 (m, 1 H, H4
C5H3N), 8.61 (m, 2 H, H3,5 C5H3N), 7.63–7.45 (m, 10 H, Ph), 5.80,
5.56, 5.20 (m, 6 H, OCH2, CHPh), –19.73 (s, 1 H, IrH) ppm.
13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 171.5 (s,
OCN), 171.1 (s, OCN), 163.0 (s, CO), 146.0 (s, C2,6 C5H3N), 145.6
(s, C2,6 C5H3N), 145.2 (s, C4H C5H3N), 136.6 (s, ipso-Ph), 135.4 (s,
Synthesis of Complexes [Rh(CH3)I(CO)(κ3-N,N,N-R-pybox)][PF6]
[R = iPr (10), Ph (11)]: A suspension of [Rh(CO)(κ3-N,N,N-R-
pybox)][PF6] (0.346 mmol) in CH3I (5 mL) was stirred at 30 °C for
5 min. The excess of reagent was then removed under reduced pres-
sure and the resulting solid residue was dissolved in dichlorometh-
ane (5 mL) and subjected to silica gel column chromatography. Elu-
tion with a dichloromethane/methanol mixture gave a yellow band
from which complexes 10 and 11 were isolated as yellow solids after
solvent removal. 10: Eluted with dichloromethane/methanol (10:1).
Yield: 80% (0.201 g). Colour: yellow. C19H26F6IN3O3PRh (719.20):
ipso-Ph), 130.4, 130.2, 130.1, 129.4, 129.3, 128.9, 128.9 (s, C3,5
H
C5H3N, Ph), 80.7 (s, OCH2), 74.7 (s, OCH2), 71.9 (s, CHPh), 70.1
(s, CHPh) ppm.
Synthesis of Complexes [IrCl(η1-CH2CH=CH2)(CO)(κ3-N,N,N-R-
pybox)][PF6] [R = iPr (14), Ph (15)]: Allyl chloride (0.025 mL,
0.30 mmol) was added to a solution of complex 1 or 2 (0.1 mmol)
in 10 mL of dichloromethane. The solution was stirred at room
calcd. C 31.73, H 3.64, N 5.84; found C 31.72, H 3.14, N 6.52. IR
(KBr): ν = 2096 (CO), 843 (PF ) cm–1. Conductivity (acetone, temperature. The resulting yellow solution was then concentrated
–
˜
6
20 °C): 110 Ω–1 cm2 mol–1. H NMR (300 MHz, CD2Cl2, 20 °C): δ to about 3 mL and 30 mL of a mixture of diethyl ether and hexane
1
= 8.58 (t, JH,H = 8.0 Hz, 1 H, H4 C5H3N), 8.25 (m, 2 H, H3,5 (1:3) was added to yield a yellow solid, which was washed with the
C5H3N), 5.12–4.87 (m, 4 H, OCH2), 4.57 (m, 1 H, CHiPr), 4.28
same solvent mixture (3×5 mL) and dried under reduced pressure.
(m, 1 H, CHiPr), 2.23 (m, 1 H, CHMe2), 2.10 (m, 1 H, CHMe2), 14: Reaction time: 1 h. Yield: 85% (0.063 g). Colour: yellow.
1.40 (d, 2JH,Rh = 1.5 Hz, 3 H, RhMe), 1.05–0.93 (m, 12 H, CHMe2)
ppm. 13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 185.5
(d, JC,Rh = 59.8 Hz, CO), 167.6 (s, OCN), 167.3 (s, OCN), 145.1,
144.4 and 144.3 (s, C4H and C2,6 C5H3N), 129.8 (s, C3,5H C5H3N),
129.6 (s, C3,5H C5H3N), 74.8, 74.7, 70.9 and 70.3 (s, OCH2 and
CHiPr), 19.2 (s, CHMe2), 19.0 (s, CHMe2), 16.2 (s, CHMe2), 15.4
(s, CHMe2), 10.3 (d, JC,Rh = 18.3 Hz, RhMe) ppm. 11: Eluted with
C21H28ClF6IrN3O3P (743.11): calcd. C 33.94, H 3.80, N 5.65;
found C 34.05, H 3.99, N 5.77. IR (KBr): ν = 2079 (CO), 846
˜
(PF ) cm–1. IR (CH Cl ): ν = 2070 (CO) cm–1. Conductivity (ace-
–
˜
6
2
2
tone, 20 °C): 126 Ω–1 cm2 mol–1. H NMR (300 MHz, [D6]acetone,
20 °C): δ = 8.78 (t, JH,H = 8.0 Hz, 1 H, H4 C5H3N), 8.53 (d, JH,H
= 8.0 Hz, 1 H, H3,5 C5H3N), 8.52 (d, JH,H = 8.0 Hz, 1 H, H3,5
C5H3N), 5.84 (m, 1 H, HC=CH2), 5.32 (m, 4 H, OCH2), 4.87 (m,
1
dichloromethane/methanol (50:1). Yield: 74% (0.202 g). Colour: 1 H, HC=CH2), 4.81 (m, 1 H, HC=CH2), 4.64 (m, 1 H, CHiPr),
yellow. C25H22F6IN3O3PRh (787.23): calcd. C 38.14, H 2.82, N
4.56 (m, 1 H, CHiPr), 3.18 (m, 1 H, IrCH2), 2.34 (m, 1 H, IrCH2),
2.28 (m, 2 H, CHMe2), 1.16 (d, JH,H = 7.0 Hz, 3 H, CHMe2), 1.11
(d, JH,H = 7.0 Hz, 3 H, CHMe2), 1.09 (d, JH,H = 6.7 Hz, 3 H,
CHMe2), 1.07 (d, JH,H = 6.7 Hz, 3 H, CHMe2) ppm. 13C{1H}
5.34; found C 38.99, H 2.61, N 5.46. IR (KBr): ν = 2099 (CO), 842
˜
–
1
(PF6 ) cm–1. Conductivity (acetone, 20 °C): 128 Ω–1 cm2 mol–1. H
NMR (300 MHz, [D6]acetone, 20 °C): δ = 8.90 (t, JH,H = 8.0 Hz,
1 H, H4 C5H3N), 8.66 (m, 2 H, H3,5 C5H3N), 7.53 (m, 10 H, Ph), NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 171.7 (s, OCN), 171.0
2
5.65 (m, 4 H, OCH2), 5.19 (m, 2 H, CHPh), 1.18 (d, JH,Rh
=
(s, OCN), 165.9 (s, CO), 145.7 (s, C4H C5H3N or HC=CH2 allyl),
145.0 (s, C2,6 C5H3N), 144.3 (s, C2,6 C5H3N), 142.9 (s, C4H C5H3N
or HC=CH2 allyl), 129.8 (s, C3,5H C5H3N), 112.9 (s, HC=CH2 al-
lyl), 75.8 (s, OCH2), 75.1 (s, OCH2), 71.7 (s, CHiPr), 71.0 (s,
1.7 Hz, 3 H, RhMe) ppm. 13C{1H} NMR (75.48 MHz, [D6]ace-
tone, 20 °C): δ = 184.0 (d, JC,Rh = 60.4 Hz, CO), 167.7 (s, OCN),
167.3 (s, OCN), 145.6, 145.1 and 144.5 (s, Ph and C2,6 C5H3N),
606
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Eur. J. Inorg. Chem. 2006, 599–608

Carbonyliridium and -rhodium Complexes of Pybox Ligands
FULL PAPER
CHiPr), 31.2 (s, CHMe2), 30.4 (s, CHMe2), 19.3 (s, CHMe2), 18.6
(s, CHMe2), 15.8 (s, CHMe2), 15.6 (s, CHMe2), 5.9 (s, IrCH2) ppm.
15: Reaction time: 15 min. Yield: 89% (0.072 g). Colour: yellow.
C27H24ClF6IrN3O3P (811.14): calcd. C 39.98, H 2.98, N 5.18;
to the reaction temperature and stirred until completion of the re-
action. The disappearance of acetophenone was monitored by
TLC. Before the aqueous workup, an aliquot was taken and exam-
ined by 1H NMR spectroscopy. The workup of the reaction mixture
found C 39.22, H 3.16, N 5.12. FAB-MS: m/z = 666 [M+]. IR was carried out as described by Nishiyama.[10] The enantiomeric
(KBr): ν = 2069 (CO), 842 (PF ) cm–1. IR (CH Cl ): ν = 2077 excess was determined, after hydrolysis, by GC analysis with a Sup-
–
˜
˜
6
2
2
(CO) cm–1. Conductivity (acetone, 20 °C): 127 Ω–1 cm2 mol–1. 1H
NMR (300 MHz, [D6]acetone, 20 °C): δ = 8.85 (t, JH,H = 8.0 Hz,
1 H, H4 C5H3N), 8.64 (d, JH,H = 8.0 Hz, 2 H, H3,5 C5H3N), 7.70–
7.40 (4m, 10 H, Ph), 5.83 (m, 2 H, OCH2, CHPh), 5.65 (m, 1 H,
CHPh), 5.40 (m, 3 H, OCH2, HC=CH2 allyl), 5.19 (m, 1 H, OCH2),
4.64 (m, 2 H, HC=CH2 allyl), 2.57 (m, 1 H, IrCH2), 2.10 (m, 1 H,
IrCH2) ppm. 13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C): δ =
171.6 (s, OCN), 171.1 (s, OCN), 164.1 (s, CO), 145.7 (s, C4H
C5H3N or HC=CH2 allyl), 145.4 (s, C2,6 C5H3N), 145.3 (s, C2,6
C5H3N), 143.6 (s, C4H C5H3N or HC=CH2 allyl), 135.9 (s, ipso-
Ph), 135.4 (s, ipso-Ph), 131.1, 130.6, 130.4, 130.2, 129.8, 129.7 (s,
Ph, C3,5H C5H3N), 112.1 (s, HC=CH2 allyl), 81.0 (s, OCH2), 80.8
(s, OCH2), 70.8 (s, CHPh), 70.2 (s, CHPh), 5.8 (s, IrCH2) ppm.
elco β-DEX 120 chiral capillary column.
X-ray Structure Determination of 15: Single crystals suitable for an
X-ray study were obtained by slow diffusion of diethyl ether into
a solution of complex 15 in dichloromethane. An orange, prismatic
single crystal (0.50×0.25×0.17 mm), orthorhombic, space group
P212121 (determined from systematic absences) was used. Diffrac-
tion data were recorded at 293(2) K with a Nonius Kappa CCD
single-crystal diffractometer, using Cu-Kα radiation (λ = 1.5418 Å).
The crystal–detector distance was fixed at 29 mm, and a total of
2432 frames were collected using the oscillation method, with 2°
oscillation and a 60 s exposure time per frame. The data-collection
strategy was calculated with the program Collect.[15] Data re-
duction and cell refinement were performed using the programs
HKL Denzo and Scalepack.[16] Unit-cell dimensions were deter-
mined from 7669 reflections. Unit-cell parameters: a = 13.0003(8),
b = 13.4939(9), c = 17.8850(8) Å, V = 3137.5(3) Å3, Z = 4, Dcalcd.
= 1.717 gcm–3. Absorption coefficient: μ = 10.121 mm–1. A total
of 50428 reflections were collected, with 5662 independent reflec-
tions (Rint = 0.087). Data completeness was 98.7%. The software
package WINGX was used for space-group determination, struc-
ture solution and refinement.[17] The structure was solved by Pat-
terson interpretation and phase expansion using DIRDIF.[18] An
empirical absorption correction was applied using XABS2.[19] (Ra-
tio of minimum to maximum apparent transmission: 0.164460.)
Isotropic least-squares refinement on F2 was carried out using
SHELXL-97.[20] During the final stages of the refinements, all posi-
tional parameters and the anisotropic temperature factors of all the
non-H atoms were refined. The H atoms were placed geometrically
and their coordinates were refined riding on their parent atoms.
The final cycle of full-matrix least-squares refinement based on
5662 reflections and 379 parameters converged to a final value of
R1 [F2 Ͼ 2σ(F2)] = 0.0607, wR2 [F2 Ͼ 2σ(F2)] = 0.1580, R1 (F2) =
0.0656, wR2 (F2) = 0.1631. The absolute structure parameter was
Synthesis of Complexes [IrCl{η1-C(O)CH3}(CO)(κ3-N,N,N-R-
pybox)][PF6] [R = iPr (16), Ph (17)]: Acetyl chloride (0.007 mL,
0.1 mmol) was added to a solution of complex 1 or 2 (0.1 mmol)
in 10 mL of dichloromethane. The solution was stirred at room
temperature. The resulting yellow solution was then concentrated
to about 3 mL and 30 mL of diethyl ether was added to yield a
yellow solid, which was washed with diethyl ether (3×5 mL) and
dried under reduced pressure. 16: Reaction time: 40 min. Yield:
86% (0.065 g). Colour: yellow. FAB-MS: m/z = 600 [M+]. IR
(KBr): ν = 2086 (CO), 1677 (COMe), 842 (PF ) cm–1. IR
–
˜
6
(CH Cl ): ν = 2079 (CO) cm–1. Conductivity (acetone, 20 °C):
˜
2
2
120 Ω–1 cm2 mol–1. 1H NMR (300 MHz, [D6]acetone, 20 °C): δ =
8.89 (t, JH,H = 8.0 Hz, 1 H, H4 C5H3N), 8.63 (d, JH,H = 8.1 Hz, 1
H, H3,5 C5H3N), 8.54 (d, JH,H = 8.1 Hz, 1 H, H3,5 C5H3N), 5.35
(m, 4 H, OCH2), 4.90 (m, 1 H, CHiPr), 4.56 (m, 1 H, CHiPr), 2.62
(s, 3 H, COMe), 2.41 (m, 1 H, CHMe2), 2.23 (m, 1 H, CHMe2),
1.13 (m, 9 H, CHMe2), 0.88 (d, JH,H = 6.8 Hz, 3 H, CHMe2) ppm.
13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C, major isomer): δ
= 196.9 (s, COMe), 172.1 (s, OCN), 171.9 (s, OCN), 164.9 (s, CO),
146.3 (s, C4H C5H3N), 144.8 (s, C2,6 C5H3N), 144.4 (s, C2,6
C5H3N), 130.2 (s, C3,5H C5H3N), 129.5 (s, C3,5H C5H3N), 75.4 (s,
OCH2), 75.1 (s, OCH2), 71.6 (s, CHiPr), 71.1 (s, CHiPr), 46.2 (s,
COMe), 31.3 (s, CHMe2), 30.4 (s, CHMe2), 19.1 (s, CHMe2), 18.8
(s, CHMe2), 15.6 (s, CHMe2), 14.6 (s, CHMe2) ppm. 17: Reaction
time: 10 min. Yield: 91% (0.074 g). Colour: yellow. C26H22ClF6Ir-
found to be 0.053(19). The function minimised was [(ΣwFo2–Fc )/
2
Σw(Fo2)]1/2, where w = 1/[σ2(Fo2) + (0.1216P)2] with σ(Fo2) from
counting statistics and P = [Max(Fo2,0) + 2Fc ]/3. Atomic scat-
2
tering factors were taken from the International Tables for X-ray
Crystallography.[21] Final difference electron density maps showed
no features outside the range +1.135 to –0.764 eÅ–3. Geometrical
calculations were made with PARST.[22] The crystallographic plots
were made with PLATON.[23] CCDC-278506 (15) contains the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
N3O4P (813.12): calcd. C 38.41, H 2.73, N 5.17; found C 37.97, H
–
2.60, N 4.98. IR (KBr): ν = 2080 (CO), 1669 (COMe), 844 (PF )
˜
6
cm–1. IR (CH Cl ): ν = 2087 (CO) cm–1. Conductivity (acetone,
˜
2
2
20 °C): 123 Ω–1 cm2 mol–1. 1H NMR (300 MHz, [D6]acetone,
20 °C): δ = 8.93 (t, JH,H = 8.0 Hz, 1 H, H4 C5H3N), 8.71 (d, JH,H
= 8.0 Hz, 1 H, H3,5 C5H3N), 8.62 (d, JH,H = 8.0 Hz, 1 H, H3,5
C5H3N), 7.80–7.40 (m, 10 H, CHPh), 5.85 (3 H), 5,53 (1 H), 5.42
(1 H), 5.21 (1 H) (4×m, OCH2, CHPh), 1.92 (s, 3 H, COMe) ppm.
13C{1H} NMR (75.48 MHz, [D6]acetone, 20 °C): δ = 195.9 (s, Acknowledgments
COMe), 172.3 (s, OCN), 171.4 (s, OCN), 163.3 (s, CO), 146.1 (s,
C4H C5H3N), 145.2 (s, C2,6 C5H3N), 145.1 (s, C2,6 C5H3N), 135.6
This work was supported by the Ministerio de Ciencia y Tecnología
(s, ipso-Ph), 135.1 (s, ipso-Ph), 131.0, 130.7, 130.6, 130.2, 130.2,
130.1, 129.7, 129.4 (s, C3,5H C5H3N, Ph), 81.0 (s, OCH2), 80.7 (s,
OCH2), 71.0 (s, CHPh), 70.4 (s, CHPh), 46.1 (s, COMe) ppm.
of Spain (project BQU2003-00255) and FICYT (project PR-01-
GE-4). P. P. thanks the Ministerio de Educación y Cultura (MEC)
of Spain for the award of a PhD grant.
General Procedure for Catalytic Reactions: A 10-mL flask was
charged with the complex catalyst (0.04 mmol, 1.0 mol%), iPr-py-
box (when applicable; 0.16 mmol, 4.0 mol%) and acetophenone
(4.00 mmol) under dry nitrogen. After cooling to –10 °C, Ph2SiH2
(6.4 mmol) was added dropwise. The reaction mixture was warmed
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[2] C.-X. Zhao, M. O. Duffey, S. J. Taylor, J. P. Morken, Org. Lett.
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Eur. J. Inorg. Chem. 2006, 599–608
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
607

D. Cuervo, J. Díez, M. P. Gamasa, J. Gimeno, P. Paredes
FULL PAPER
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[7]
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1
The H and 13C{1H} NMR signals for the pybox ligands pro-
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[19] S. Parkin, B. Moezzi, H. Hope, J. Appl. Crystallogr. 1995, 28,
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[20] G. M.Sheldrick, SHELXL-97, Program for the Refinement of
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[21] International Tables for X-ray Crystallography, Kynoch Press,
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[22] M. Nardelli, Comput. Chem. 1983, 7, 95–98.
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Received: July 28, 2005
Published Online: December 20, 2005
608
www.eurjic.org
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Eur. J. Inorg. Chem. 2006, 599–608